Tweets of the week: Serena's selfie, Wozniacki celebrates Halloween

Serena Williams has nightmares, Maria Sharapova makes a case for getting rid of the selfie stick and Caroline Wozniacki and Alexandr Dolgopolov celebrate Halloween. Here are the best dispatches from Twitter this week:

I just has a nightmare so scary I woke up crying. I am starting to think sleep is only for the brave. I don't think I can go back to sleep.
— Serena Williams (@serenawilliams) October 30, 2014